V-253458 | NTLM must be prevented from falling back t...

Microsoft Windows 11

NTLM must be prevented from falling back to a Null session

STIG ID: WN11-SO-000180 | SRG: SRG-OS-000480-GPOS-00227 | Severity: Medium | CCI: CCI-000366 | Vulnerability ID: V-253458

Description

NTLM sessions that are allowed to fall back to Null (unauthenticated) sessions may gain unauthorized access.

Check

C-56911r829456_chk

If the following registry value does not exist or is not configured as specified, this is a finding:Registry Hive: HKEY_LOCAL_MACHINERegistry Path: \SYSTEM\CurrentControlSet\Control\LSA\MSV1_0\Value Name: allownullsessionfallbackValue Type: REG_DWORDValue: 0

Fix

F-56861r829457_fix

Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Network security: Allow LocalSystem NULL session fallback" to "Disabled".